Whether it's EJB Module or you are working on some other application with WebLogic Server; it requires a configuration Process; you can go through the links given below:
[http://techworldrocks.wordpress.com/2012/08/16/configure-log4j-logging-for-weblogic-server-log/][1]
[http://docs.oracle.com/cd/E24329_01/web.1211/e24428/config_logs.htm#i1014785][1]